This project is designed to elucidate the magnitude and, hopefully, something of the mechanisms and controls of the ion fluxes to and from the skeleton. The studies prinipally involve (but are not limited to) calcium, inorganic phosphate, lactate, and potassium. The model systems employed principally (but not exclusively) are calvaria of newborn rat pups or embryonic chickens. The influences of hormones and metabolic inhibitors are under investigation. Modified Ussing chambers permit the evaluation of unidirectional fluxes across periosteal or endosteal membranes. In some instances ion gradients between bone fluid and surrounding medium can also be measured. BIBLIOGRAPHIC REFERENCES: Scarpace, P.J. and W.F.Neuman: The blood:bone disequilbrium. I. The active accumulation of K ion into the bone extracellular fluid. Calc. Tiss. Res. 20, 137-149 (1976). Scarpace, P.J. and W.F. Newuman: The blood:bone disequilibrium. II. Evidence against active accumulation of calcium or phosphate into the bone extracellular fluid. Calc. Tiss. Res. 20, 151-158 (1976).